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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6f1fe5687a84bf8823034d303414934f5e8e8f10e8e096068a25542c40ef2e8' 
  AND token = 'tDeVPSgAvMqL5OpEVmIxQm1Wm1LhSRs/j5bejSL7mZA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}